1. Field of the Invention
The present invention relates to a novel pyrimidone compound and more specifically to a useful and novel pyrimidone compound and pharmaceutically acceptable salt thereof exhibiting excellent gastric acid secretion inhibitory effect and cytoprotective effect.
2. Description of the Prior Art
Up to now, there have been known some pharmaceutically useful compounds which have excellent antagonistic effect in respect of H.sub.2 receptor and gastric acid secretion inhibitory effect. For instance, Cimetidine, Ranitidine, Famotidine and Roxatidine are commercially available and many other compounds are disclosed in, for instance, Japanese Patent Unexamined Publication (hereunder referred to as "J.P. KOKAI") Nos. 60-255756; 61-85365; 61-207375 and 60-228465. One of principal effects of these compounds is acid secretion inhibitory effect due to antagonistic effect in respect of histamine H.sub.2 receptor and they show a remarkable curative effect of gastric ulcers. However, if the medication is stopped after healing, such gastric ulcer recurs because of so-called rebound phenomenon, which becomes an important clinical problem. In order to prevent such gastric ulcer from recurring, an agent having acid secretion inhibitory effect such as an antagonist in respect of histamine H.sub.2 receptor and a drug having a defence effect for the mucous membrane of alimentary canals have been simultaneously administered or after stopping the treatment with an antiulcer, the treatment is continued with a drug having defence effect. However, the use of only an attack factor inhibiting agent such as an acid secretion inhibitor is insufficient from the clinical point of view.